<span>Plate tectonics suggest that the lithosphere floats and moves on the asthenosphere.</span>
Due that the velocity is constant that means that friction force is equal to the force exert by you, otherwise the refrigerator will accelerate or decelerate and in both cases velocity will not be constant.
So then the friction force between refrigerator and floor is 150 Newtons.
Answer:
a

b
The value is 
Explanation:
From the question we are told that
The mass is
The spring constant is 
The instantaneous speed is 
The position consider is x = 0.750A meters from equilibrium point
Generally from the law of energy conservation we have that
The kinetic energy induced by the hammer = The energy stored in the spring
So

Here a is the amplitude of the subsequent oscillations
=> 
=> 
=> 
Generally from the law of energy conservation we have that
The kinetic energy by the hammer = The energy stored in the spring at the point considered + The kinetic energy at the considered point

=> 
=> 